A conventional optical disc drive made recording in accordance of a recording method specified in a standard. Further, even in a recording method of a conventional disc drive, before recording was made, a test pattern was recorded in the trial write area on a disc using various types of laser power and an output value that is suitable for laser was fixed based on the reproduction result of the test pattern.
However, in the recording method as specified in the standard, a problem occurred in some cases according to the type of the disc, the shape of the drive, or the data recorded in the disc.
Usually, the sensitivity of a disc to laser beam is not uniform over the whole disc surface. Further, laser has a characteristic that the laser is subject to the influence of ambient temperature by the heat the laser itself emits and the heat generated from a disc drive circuit and the output changes.
Based on this characteristic, a recording method of Disc at Once specified in the standard and the point at issue are described.
This Disc at Once recording method is used, for example, when data, such as a video and an audio, is recorded in a DVD-R and the recording data realizes reproduction compatibility in a DVD video player. Further, this recording method specifies that data is continuously recorded without being interrupted halfway from the external surface to the internal surface of a disc.
Accordingly, in this recording method, recording must be continued without evaluating the sufficient recording quality of recorded data until all data is recorded. The reason why the recorded data cannot be evaluated sufficiently is that usually, a recording head and a reproducing head are integrated in an optical disc drive.
The most reliable method for evaluating recording quality is to reproduce recorded data. However, in a head that shares recording and reproduction, the reproduction can be made only when the recording is stopped. Accordingly, because a conventional optical disc drive cannot interrupt the recording in the recording method, such as above Disc at Once, reliable recording quality is not evaluated. Accordingly, it was difficult to maintain appropriate recording quality concerning the whole data that was recorded.
When the size of a series of data to be recorded is large and continuous recording lasts for a long time in particular, sufficient recording quality cannot be evaluated in course of recording. Accordingly, the laser output cannot be controlled appropriately and there was a problem of the deterioration or unevenness of recording quality. Further, because the temperature inside a disc drive becomes extremely high due to continuous recording, laser cannot be used under good temperature characteristics. Accordingly, the maintenance of the recording quality was difficult. Further, the maintenance of the recording quality was difficult in a compact disc drive of which the mounting of a cooling means, such as a fan, also causes a cost increase and that has no room for space and is limited in a power supply.
There were some conventional disc drives, for example, as disclosed in Japanese Unexamined Patent Publication No. 2001-34947, that execute recording and making adjustments so as to satisfy the optimum recording condition evaluating recording quality. However, these conventional disc drives made the adjustments between recording and recording choosing a period during which data is not transferred from a host machine connected to a disc drive.
However, when the data is transferred incessantly from the host machine, such as in Disc at Once recording, the recording must be continued incessantly. Accordingly, it was difficult to make a recording in a good recording condition after the recording quality is checked sufficiently during that time.
This was a problem when real time data, such as a video and an audio, is recorded in particular. When the real time data is recorded, the recording data itself that is recorded becomes an original source. That is, after all data have been recorded, it is impossible to evaluate recording quality, and to redo the recording from the beginning if the recording quality is bad. Because of such reason, the conventional disc drive could not take corrective action for real time recording. Further, even in the case of non-real time recording that enables undoing of recording, the time for undoing the recording occurs. In a medium, such as a DVD-R, in which a disc enables recording only once, a new disc is required.
As described above, when a series of data, such as Disc at Once recording, must be recorded continuously in particular, such Disc at Once recording, it was difficult for a conventional disc drive to satisfactorily maintain the recording quality of the whole recorded data. Further, accordingly, the real time recording of a video and an audio in which the recording data itself becomes an original source at once is not suitable for a recording method, such as the Disc at Once recording, in which a series of data must be recorded continuously. The recording of real time data into a disc, such as a DVD-R in particular, in which recording is enabled only once was difficult.